MOTIF Boundary Conditions


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The following are guidelines for the boundary conditions for the MOTIF coupled models experiments. These same guidelines will be proposed for PMIP 2.

 

We require each group to document precisely what it does!

 

Analysis will be performed over the final 100-200 years of all the simulations,
after the stage when the trends are small.

 

 

Pre-industrial control run

                 
Boundary conditions Value
Vegetation OA OAV
Fixed (1) Interactive
Ice sheets Modern
Topography, coastlines Modern
Greenhouse gases CO2 CH4 N20 CFC 03
Pre-industrial (around 1750)
280 ppm 760 ppb 270 ppb 0 Modern - 10 DU
Insolation (2) Solar constant = 1365 W/m2
Eccentricity Obliquity Angular precession
0.016724 23.446 ° 102.04 °
Initial ocean state Modern
Initialize 3-D ocean temperature and salinity from the Levitus 1998 datasets
Model spinup See note 3 below

Notes

The minimum requirements for PMIP 1 were that we all used the exact same change in forcing.

For MOTIF and PMIP 2, we recommend that any group embarking on new control simulations use the above recommendations. It is important to have pre-industrial CTRL simulations.

  1. Vegetation will be provided for anyone interested.
  2. Orbital parameters values are for 1950 AD.
  3. Each group has its own spinup methodology, which we ask they document.

    The model should be run long enough for any trends to be small, and the control run should be at least as long as any anomaly integrations.
 

Mid-holocene 6k BP

                 
Boundary conditions Value
Vegetation OA OAV
Same as control run Interactive
Ice sheets Same as control run
Topography, coastlines Same as control run
Greenhouse gases CO2 CH4 N20 CFC 03
280 ppm 650 ppb 270 ppb 0 Same as control run
Insolation (1) Same as control run
Eccentricity Obliquity Angular precession
0.018682 24.105 ° 0.87 °
Initial ocean state Initialize 3-D ocean temperature and salinity either from the Levitus 1998 datasets or from year 100 of the control run
Model spinup Same as control run

Notes

  1. Insolation 

    Make sure you check the insolation related tables at the end of this page!

 

Last glacial maximum 21k BP

                 
Boundary conditions Value
Vegetation OA OAV
Same as control run Interactive
Ice sheets (1) ICE-5G
Topography, coastlines (2) From ICE-5G data set
Greenhouse gases (3) CO2 CH4 N20 CFC 03
185 ppm 350 ppb 200 ppb 0 Same as control run
River outflow (4) Modified according to a river pathway map
Ice sheet melt (5) Same as control run, or
add excess LGM freshwater
Insolation Same as control run
Eccentricity Obliquity Angular precession
0.018994 22.949 ° 114.42 °
Initial ocean state Mean ocean salinity:
Same as control run
Option 1: same as for control run (warm ocean state)
but see model spinup below

Option 2: cold ocean state from existing LGM simulation
Model spinup See note 5 below

Notes

  1. We will use a new ice sheet reconstruction, ICE-5G, provided by Dick Peltier. The largest difference between ICE-5G and the previous version (ICE-4G), used in the first phase of PMIP, is that it takes into account new information about the extent of glacial maximum ice sheets in Eurasia provided by the QUEEN project.
    The data will be provided on the same grid as ICE-4G. Boundary conditions will then be adapted to the model grid using the same protocol used in PMIP 1.

  2. Use the land-sea mask and change in topography supplied by Dick Peltier, consistent with the ice sheet in ICE-5G, rather than a simple lowering using present day bathymetry (change land height, don't make oceans shallower). The data set will tell what increase in land elevation has to be applied to each grid cell (land is then cells above LGM 0 level).
    Check narrow or low depth straits carefully!

  3. Greenhouse gases

    Monnin, E., A. Indermuhle, A. Dallenbach, J. Fluckiger, B. Stauffer, T.F. Stocker, D. Raynaud, and J.M. Barnola, Atmospheric CO2 concentrations over the last glacial termination, Science, 291 (5501), 112-114, 2001.

    Dallenbach, A., T. Blunier, J. Fluckiger, B. Stauffer, J. Chappellaz, and D. Raynaud, Changes in the atmospheric CH4 gradient between Greenland and Antarctica during the Last Glacial and the transition to the Holocene, Geophysical Research Letters, 27 (7), 1005-1008, 2000.

    Fluckiger, J., A. Dallenbach, T. Blunier, B. Stauffer, T.F. Stocker, D. Raynaud, and J.M. Barnola, Variations in atmospheric N2O concentration during abrupt climatic changes, Science, 285 (5425), 227-230, 1999.

  4. River routing

    Sandy Harrison has provided river pathways estimates at 5-minute resolution using HYDRA (Harrison, Bartlein, Coe and Sickel, in prep.).

  5. Ice sheet melt

    Provide a simple solution for models in which something has to be done.
    For models with only a global closure of the water budget, introduce this excess fresh water in the global estimate to ensure water conservation in the model.

  6. Each group has its own spinup methodology, which we ask they document.

    If initializing from modern conditions (Option 1):
    1. Option 1a: we recommend doing a 100-year Haney forced run, restoring the SSTs to those of a slab model LGM anomaly SSTs.
    2. Option 1b: or 100-year Haney forced run, restoring to CLIMAP LGM anomaly SSTs.
    3. Option 1c: or ocean-only stage restoring SSTs to slab or CLIMAP LGM

    4. Option 1d: or just run it (brute force approach)!

    For both Options 1 and 2:
    Run the OAGCM (initialized from either the end of Option 1, or from the cold state of an existing LGM simulation) for long enough for any trends to be small.
 

Trend diagnosis

The models will have to be run for long enough for any trends to be small (at least 100 years of spinup).

Use the annual mean time series of the following variables to summarize large-scale model behaviour and trends:

 

About insolation computation

In the following, we provide tables and information concerning insolation in order to help you check your insolation code.

All the results we give have been obtained using:

All the values of insolation are given in W/m2. They are given at every 10 degrees of latitude (no latitudinal band average is done!). All the computations follow the method proposed by Berger (JAS, 1978) and are based on an expansion accurate to order e**3 for the computation of the true longitude (lambda, angle defining the Earth position relative to the Vernal Equinox).

Dates of Equinoxes and Solstices

Date of Present orbit 6 kyr BP orbit 21 kyr BP orbit
Length of year (days)
365 360 365 360 365 360
Vernal equinox 21.00 March
Summer solstice 21.73 June 22.46 June 22.45 June 23.17 June 21.32 June 22.06 June
Automnal equinox 23.30 Sept 24.74 Sept 19.56 Sept 21.06 Sept 23.52 Sept 24.96 Sept
Winter solstice 22.05 Dec 23.26 Dec 17.61 Dec 18.89 Dec 22.65 Dec 23.86 Dec
Perihelion 2.85 Jan 4.91 Jan 20.42 Sept 21.90 Sept 15.51 Jan 17.39 Jan
Aphelion 4.35 July 4.91 July 21.92 March 21.90 March 17.01 July 17.39 July

Insolation monthly means

The insolation values for monthly means depend on the length of the year and on the reference date used (21.00 March vernal equinox in the following table).

Note: the text files you can download in the tables below have unix-style end of lines. If you are using Windows, you can view them directly in your browser, or you can download them and display their content with WordPad.

File type Present orbit 6 kyr BP anomaly 21 kyr BP anomaly
Length of year (days)
365 360 365 360 365 360
HTML www www www www www www
TEXT txt txt txt txt txt txt

Insolation mid-month values

The insolation mid-month values are obtained as daily mean insolation values in W/m2 and are computed at fixed true longitudes with longitude increments of 30°, starting from the vernal equinox (Berger, JAS, 1978) ... i.e. around the 20th of each month.

Using this definition, we have:

Longitude Corresponds to Abbreviation
0 Vernal equinox VE
90 Summer solstice SS
180 Autumnal equinox AE
270 Winter solstice WS

These tables of mid-month values:

File type Present orbit 6 kyr BP anomaly 21 kyr BP anomaly
HTML www www www
TEXT txt txt txt

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